Oligomerization of olefins with boron trifluoride

ABSTRACT

A PROCESS IS PROVIDED FOR OLIGOMERIZING OLEFINS, TO OBTAIN A FLUID IN WHICH THE TRIMER TO TETRAMER AND HIGHER RATIO IS AT LEAST FOUR, WHICH COMPRISES: CONTACTING SAID OLEFINS IN A REACTION ZONE WITH A CARBOXYLIC ACID-PROMOTED BORON TRIFLUORIDE CATALYST, SAID CARBOXYLIC ACID HAVING AT LEAST 3 CARBON ATOMS, IN A MOLE RATIO OF PROMOTER TO OLEFINS OF FROM ABUT 0.005:1 TO ABOUT 0.05:1 AND AT A TEMPERATURE OF FROM ABOUT 0*C., TO ABOUT 20*C., IN THE PRESENCE OF FREE BORON TRIFLUORIDE.

United States Patent 3,769,363 OLIGOMERIZATION 0F OLEFINS WITH BORONTRIFLUORIDE James A. Brennan, Cherry Hill, N.J., assignor to Mobil OilCorporation No Drawing. Filed Mar. 13, 1972, Ser. No. 234,370 Int. Cl.C07c 3/18 US. Cl. 260683.15 B 5 Claims ABSTRACT OF THE DISCLOSURE Aprocess is provided for oligomerizing olefins, to obtain a fluid inwhich the trimer to tetramer and higher ratio is at least four, whichcomprises: contacting said olefins in a reaction zone with a carboxylicacid-promoted boron trifluoride catalyst, said carboxylic acid having atleast 3 carbon atoms, in a mole ratio of promoter to olefins of fromabut 0.005z1 to about 0.05:1 and at a temperature of from about 0 C., toabout 20 C., in the presence of free boron trifluoride.

BACKGROUND OF THE INVENTION (1) Field of the invention This inventionrelates to the oligomerization of olefins and, in one of its aspects,relates more particularly to a reproducible process for oligomerizingolefins to obtain a product having a trimer to tetramer and higher ratioof at least four. Still more particularly, in this aspect, the inventionrelates to an improved process for the oligomerization of l-olefins, orolefin fractions, for the manufacture of synthetic fluid lubricants,suitable for many industrial applications, employing boron trifluoridecatalysts under conditions in which the oligomerization is so conductedthat polyolefins predominating in trimer yield are obtained.

(2) Description of the prior art As is known to those skilled in theart, boron trifluoride, per se, is a poor catalyst for polymerization oroligomerization of olefins unless it is employed in conjunction with asuitable promoter. For this purpose, the prior art has suggested, amongother materials, the use of alcohol-promoted or water-promoted borontrifluoride. In this respect, polyolefins predominating in trimer yieldare considered essential in order to prepare synthetic fluid lubricantsespecially when utilized as a base for such materials as hydraulicfluids to be used over a wide temperature range.

SUMMARY OF THE INVENTION In accordance with the present invention anovel method is provided for conducting the oligomerization of C to Colefins, in which a relatively high trimer yield is obtained in theresulting product. Such significant oligomerization control, withimproved trimer yield, is achieved by contacting the olefins in areaction zone with a carboxylic acid-promoted boron trifluoridecatalyst, in which the carboxylic acid contains at least about 3 carbonatoms, in a mole ratio of promoter to olefins of from about 0.005 :1 toabout 0.05 :1 and at a temperature of from about 0 C. to about 20 C inthe presence of free boron trifluoride.

In carrying out the above-described oligomerization as previouslyindicated, a carboxylic acid having at least 3 carbon atoms per moleculeis employed as a promoter for the boron trifluoride catalyst. In thisrespect, lower carbon-content carboxylic acids, for example, aceticacid, cannot be successfully employed because of the high melting pointof the boron trifluoride adducts that are formed. Another criticalfeature of the novel process resides in ice the necessity formaintaining the oligomerization temperature not higher than about 20 C.,inasmuch as it is found that at temperatures above about 20 C. theyields of the desired trimer and higher oligomers are low andsubstantial amounts of carbonyl are incorporated into the oligomers thusimpairing their usefulness.

As previously indicated, the oligomerization is carried out in acarboxylic acid promoter to olefin mole ratio of from about 0.005 :1 toabout 0.05 :1 within the aforementioned range of from about 0' C. toabout 20 C. In preferred applications, the oligomerization is carriedout in a carboxylic acid promoter to olefin mole ratio of from about0.005 :1 to about 0.015z1, and at a temperature of from about 5 C. toabout 15 C. In a still further preferred modification, theoligomerization process is so conducted that free monomer and dimer arefirst removed from the oligomerized olefin product by distillation andthe remaining product thus obtained is then subjected to hydrogenation.

DESCRIPTION OF SPECIFIC EMBODIMENTS The carboxylic acids suitable foruse in this novel process may be illustrated by the following examples.Boron trifluoride is bubbled into a mixture of valeric acids until onemolar equivalent of the halide is absorbed. The formation of theequimolar adduct is found to be highly exothermic and requires strongcooling. The temperature during this preparation is held below 50 C. Theresulting promoter solution, C H O -BF (Example 1 of Table 1), is thenprogressively cooled with stirring and its freezing point determined asbeing less than 70 C. In Examples 2-9 (Table 1) other carboxylic acidswere substituted for the mixed valeric acids and in experiments entirelysimilar to the above the freezing point of the adduct was determined asshown in Table 1. The adduct of acetic acid C H O -BF has a freeze pointof 27 C. (Example 2) and is excluded from use in this process. All ofthe other acids formed adducts which are liquid over the temperaturerange of 0-20 C. and may be used in this process.

The following examples and associated data will serve to illustrate thenovel improved process of the present invention for the oligomerizationof olefins, to obtain products in which the trimer to tetramer andhigher ratio is at least four, employing carboxylic acid-promoted borontrifluoride catalysts in which the carboxylic acid has at least 3 carbonatoms and in the aforementioned mole ratio of promoter to olefins offrom about 0.005 :1 to about 0.05 :1 and at temperatures from about 0 C.to about 20 C., in the presence of free boron trifluoride.

The novel process of the present invention can be illustrated by thefollowing catalyzed oligomerization of 1- decene employing borontrifluoride catalysts in conjunction with mixed valeric acids as apromoter for the purpose of obtaining a polyolefin product ofpredominantly increased trimer yield.

TABLE I.FREEZE POINTS OF BORON TRIFLUORIDE- CARBOXYLIC ACID EQUIMOLARADDUCTS The mixed valeric acids-boron trifluoride promoter (Example 1 ofTable l) and a boron trifluoride saturated l-decene stream are meteredseparately and simultaneously in a ratio of 0.009 mole/ 100 g. (Example10) into a clean, dry, glass-lined vessel maintained at 10 C. andpressured with boron trifluoride to 2-4" Hg. The rate of addition isdetermined by the cooling capacity of the equipment. The vessel isfilled, held at the above temcatalyst oligomerization resulted in asatisfactory improved trimer yield.

The reproducibility of the process and the shelf lives of the acid-borontrifluoride adducts are excellent. A l-decene oligomerization withisovaleric acid adduct stored perature and pressure until about 85percent of the 5 foraperiod of 35 days exactly duplicated theperformance decene has been converted and it is then quenched, water ofthe fresh adduct, as shown in the following table: washed until neutraland finally distilled to remove monomer and dimer. The trimer accountsfor greater than 050 plus olefinic, 80 percent of the C30 Plus Productggtzduct Conny? Oligomer distribution KV, cs.

As shown in Table 2, increasing the promoter acid conda 's percent DimerTrimer Residual 210 F. -40 F. centration (Example 11) results inincreased monomer 0 8M 19 69 12 386 2,008 conversion in unit time withno effect upon either the 35 86.2 18 c7 14 3.83 2,011 degree ofpolymerization or the product quality. It will be noted from the tablethat the conversions at this tem- It will be understood that althoughthe process of the perature and at these promoter concentrations can bepresent invention has been described with preferred emmade comparablethrough longer hold times. 'bodiments, various modifications andadaptations thereof TABLE 2 Oligomer distribution (wt. percent) 070 plusoleflnic Conv., KV, cs. Yield, Promoter-131%., Temp Time, Min. wt. wt.mole/100 g. 010 add hold percent Dimer Trimer Residual 210 F. 40 F.percent;

Example number:

10 0.009 mixed valerlcs 10 74 60 66 68 12 240 83 21 66 13 3.8 2,012 05.5

11 0.014 mixed valeries 10 66 60 87 1e 09 12 3.8 2,008 70.4

12 do 50 c0 01 45 52 3 3.7 1,751 33.5

12 do l0 66 60 92 7 50 a7 4.4 2,905 85.5

14 0009 water 15 44 60 97 4 01 5.0 5,540 93.6

1s .008 ethanol 15 4c 60 54 11 as 51 5.2 4, 741 48.0

16.. 0.01 acetic acid 15 48 120 24 43 47 10 13. 6

17 0.013 propionic acid (34)--- 10 49 60 76 22 68 11 3.7 1,780 60.0

In contrast with water and alcohol promoted oligomermay be resorted towithout departing from the spirit and izations, reactions with the C andhigher carboxylic scope of the invention as those skilled in the artwill readacids of the present process result in decreasing decene ilyunderstand. conversions with increasing temperatures. The average 35 Iclaim: decene conversion is found to be 87 percent at 10 C. 1. Aprocessfor oligomerizing monoolefins, having from (Example 11) but onyl 60percent at 30 C. (Example 6 to 12 carbon atoms to obtain an improvedtrimer yield, 12). Significantly, it is found that the once-throughyield which comprises: contacting said olefins in a reaction zone of Cand higher olefins is 70 percent at 10 C. (Example with a carboxylicacid-promoted boron trifluoride cata- 11) but only 34 percent at 30 C.(Example 12). The lyst, said carboxylic acid having, 5 carbon atoms anddecrease in conversion with increasing reaction temperaselected from thegroup consisting of valeric acid, iso ture is attributed to consumptionof the promoter via ester valeric acid and 2-methyl butyric acid in amole ratio formation, which is favored at high temperature. In genofpromoter to olefins of from about 0.005 :1 to about eral, therefore,oligomerization temperatures greater than 0.05:1 and at a temperature offrom about 0 C. to about about 20 C. result in low olefin conversion andhence in 20 C., in the presence of free boron trifluoride. trimer YWlilile temperatures below C- re lt i llIl- 2. A process in accordancewith claim 1 wherein said satisfactory viscosities for many applications(Example oligomerization i carri d out in a promoter to olefin becauseof the relatively low mer to tetra er a mole ratio of from about 0.005:1to about 0.015: 1. higher ratios. 3. A process in accordance with claim1 wherein said For comparative purposes,aseries of olefin oligomeriza-OLigomeriZatiOn i r ied o t t a temperature from tions were conductedbut employing, individually, water about 5 C. to about 15C.

(Example 14), alcohol (Example 15), acetic acid (Ex- 4. A process inaccordance with claim 1 wherein olefins ample 16), and propionic acid(Example 17) promoted comprise l-decene.

boron trifluoride catalysts at temperatures as shown in the 5. A processin accordance with claim 1 wherein free above Table 1. From thecomparative data thus obtained, monomer and dimer are removed from theoligomerized it will be apparent that the water-promoted- (Example 14)olefin product by distillation and the remaining product andalcoho1-promoted (Example 15) boron trifiuoride thus obtained issubjected to hydrogenation.

catalyst oligomerization resulted in relatively low trimer yield. It wasnecessary to heat trace the lines in order to References Clted deliverthe acetic acid-boron trifluoride adduct to the reac- UNITED STATESPATENTS (EXamP1e as the F 3,3s2 291 5/1968 Brennan 260--683.15 came incontact wi t e reac or maintaine a 1 solidified and settled to thebottom of the flask. After 3149178 9/1964 Hamllton 6t 260 6839 two hourscontact between liquid olefin and solid catalyst PAUL COUGHLAN, JRPrimary Examiner only 24 percent of the olefin was converted whichresulted in a C plus product yield of only 13.6 percent. On the otherhand, the use of propionic (Example 17) or valeric acid promoted(Examples 10 and 11) boron trifiuoride US. Cl. X.R.

